1. Field of the Invention
The present invention generally relates to the fields of spectroscopy, medical imaging and imaging agents. More specifically, it relates to hyperpolarized 89Y for use as nuclear magnetic resonance agents and magnetic resonance imaging agents.
2. Description of Related Art
Magnetic resonance imaging (MRI) is a technique often used in radiology to visualize the structure and function of the body, such as in neurological (brain), musculoskeletal, cardiovascular and oncological imaging (e.g., imaging of tumors). Conventional MRI techniques exploit the interaction of the intrinsic magnetic moment or spin of nuclei with an applied magnetic field. Nuclei whose spin is aligned with the applied magnetic field have a different energy state than nuclei whose spin is aligned opposed to the applied magnetic field. By applying a radio frequency radiation to the nuclei in a magnetic field, nuclei can be made to jump from a lower energy state to a higher energy state. The signals produced when the nuclei return to the lower energy state can then be measured, thereby providing information concerning the nature of the physical properties of the object being measured. In certain circumstances, the associated changed population difference can be converted into a considerable increase of the signal intensity by factors of up to several thousand—this is referred to as hyperpolarization. Hyperpolarization of nuclear spins can produce a dramatic increase in sensitivity for certain nuclei.
Dynamic nuclear polarization (DNP) is one method to achieve hyperpolarization. DNP results from transferring spin polarization from electrons to nuclei, thereby aligning the nuclear spins to the extent that electron spins are aligned. Although the idea of transferring spin polarization from electrons to nuclei by DNP to create a hyperpolarized sample has been around since the mid-1950's, applications of this technology for study of liquid samples have appeared only recently. In 2003, Ardenkjaer-Larsen et al. (2003) developed an automated method to polarize 13C nuclei at low temperatures in the presence of a stable trityl radical, then bring the sample to room temperature very quickly to perform nuclear magnetic resonance (NMR) measurements (Ardenkjaer-Larsen et al. 2003; Golman et al., 2003). This method was most practical for long T1 13C nuclei, such as non-protonated carbonyl or carboxyl carbons, in rapidly tumbling small molecules which yield NMR signal enhancements of 10,000-fold or higher. One of the more exciting applications of this technology was reported shortly thereafter by Golman et al. (2006a); Golman and Petersson (2006b) who demonstrated that it is practical to perform real time metabolic imaging of [1-13C]pyruvate, [1-13C]lactate and [1-13C]alanine in live animals using 13C chemical shift imaging.
As conventional MRI imaging agents, which are based on 1H, typically suffer from low sensitivity, identification of agents that may be hyperpolarized via DNP may offer a means to better map physiological parameters such as pH, temperature, and other indices of metabolism in vivo. MRI imaging of structural features of subjects, such as organs and tumors, may be improved using agents hyperpolarized through DNP. Commercial DNP devices derived from this technology offer new opportunities for imaging nuclei that have not ordinarily been considered possible in the past. Agents to employ in these devices for MRI are still being identified, perfected, and are in great demand.